The title says it all, if you are able to engage both the rational and emotional parts of your investor's brain, your changes of getting their signature increases immensely.
To expand on this profound statement, when you present your pitch deck, you should always contain both key ingredients:
Good Story Telling
Resonating with the emotional part of the brain, you convince your potential investors by telling them a story of your product/service, whom its serving, what pains it is resolving.
Get them to feel empathy, to feel that the story you are telling them is something something that makes them feel. If you do this successfully, it sets you up for the next ingredient, which is the business part of the investor's brain.
Support Your Story with Statistics
Once you have empathy, you need to build security, confidence, and convince of practicality. How will your story be built? Do you have numbers to back up your story?
This will end up being the meat of the pitch deck, where you will throw up TAMs, SAMs and SOMs, convince them that you can get traction to support your empathy hypotheses.